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Selenium

Where it comes from: Selenium is a trace mineral that is taken into the body through water and foods such as crab, liver, fish, poultry, Brazil nuts and wheat. The amount of selenium in food depends on where it's grown or raised — for example, the Eastern Coastal Plain and the Pacific Northwest have the lowest selenium levels in the United States.

What it'll do for you: "Selenium is an antioxidant," explains Lisa R. Young, Ph.D., R.D., author of The Portion Teller and adjunct professor of nutrition at New York University, "and helps protect cells from oxidation, which may be a contributing factor to cancer." With that in mind, selenium had been marketed in recent years as a means of preventing cancers — specifically, prostate cancer. However, the largest-ever prostate cancer prevention trial ( known as SELECT, and introduced in 2001) found it was unlikely selenium supplements — paired with another antioxidant, vitamin E — would ever produced a 25 percent reduction in prostate cancer. In October 2008, SELECT participants were told to stop taking the supplements due to lack of benefit and a possibility of potential harm

"Studies have found that people with heart disease and certain cancers often have low levels of selenium but that doesn't mean that high levels of the mineral will prevent it," Young says, pointing out that just because a correlation may work one way, doesn't mean the inverse is always true.

Doctors still suggest selenium for patients with rheumatoid arthritis and diseases of the heart and blood vessels, including stroke and hardening of the arteries and under-active thyroids. "The mineral activates your thyroid," says Young, "but, again, that doesn't mean healthy males need it in excess."

Other benefits of selenium: Healthy eyes and hair. The antioxidants of selenium help the body absorb Vitamin E, which assists in preventing cataracts from forming and plays an important role in the prevention of macular degeneration. Selenium also aids the body in processing and using proteins that are consumed. Hair is primarily composed of proteins so when the body is able to better process the proteins, hair growth will follow. Deficiencies in selenium (and zinc) often lead to hair loss.

Suggested intake: The Institute of Medicine says the Recommended Daily Allowance is 55 micrograms but studies have found that doses up to 400 mcg per day (on short-term basis) are likely safe. That's a big range so how much do men your age need to ingest?

"People often think that, if taking 100 percent is good, taking 500 percent is better but that's not the case," says Young. "Selenium is a trace mineral, which means it's present in the body in small amounts and all you need are those small amounts."

Young points out that micrograms are especially small and that most of the recommended 55 mcg quota will be satisfied by a well-balanced diet. "If you want to add a supplement, that's fine," Young says. "A pill with 50 extra micrograms isn't going to hurt you but you don't need any more than that and should avoid taking it in excess."

But how do you know if you're getting enough, let alone any in excess? In the U.S., most cases of selenium deficiency are associated with severe gastrointestinal problems such as Crohn's disease or stomach surgery. Young enforces that most males won't actually need selenium supplements. "Only people who are low in selenium would benefit," she says.

If you're going to reach for a supplement anyway, look for a reputable brand such as Nature's Bounty or Centrum. And, of course, talk to your doctor before taking anything.

Associated risks/scrutiny: The January/February issue of Nutrition Action reported that too much selenium may raise the risk of the bad types of cholesterol (LDL) and skin cancer. (Though adequate amounts of selenium have been associated with nourishing and protecting skin to extend its youthful appearance.) Long-term consumption of selenium supplements also appear to increase the chance of getting type 2 diabetes.

In addition, side effects for excess amounts of selenium include nausea, vomiting, nail changes, loss of energy and irritability. It could also result in muscle tenderness, tremor, light-headedness, facial flushing, blood clotting problems, liver and kidney problems and more.